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  • 1
    Electronic Resource
    Electronic Resource
    Low-frequency Raman scattering and structure of amorphous polymers: Stretching effect (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2949-2954 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Low-frequency Raman scattering of amorphous polymers [polyethyleneterephthalate (PET) and polymethylmethacrylate] is investigated. The low-frequency Raman band called "Boson peak'' is interpreted in terms of a noncontinuous structure, similar to that of inorganic glasses, i.e., solid amorphous polymers are composed of 50 A(ring) blobs. These are related blobs to transient entanglements in the polymer melt. Modifications induced by stretching are described for a PET film. The nature of the blob structure is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460896
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamical structure of water: Low-frequency Raman scattering from a disordered network and aggregates (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2150-2154 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Low-frequency inelastic light scattering of water is observed from a temperature equal to 80 down to −20 °C in the supercooled regime. For energies higher than 3 cm−1 it is shown that the major part of the light scattering is Raman scattering. A broadband with a maximum at 50 cm−1 is interpreted as scattering from transverse acoustic modes of a disordered network. A weaker scattering which shifts towards the Rayleigh line when the temperature decreases is well explained by Raman scattering from the oscillations of water molecule aggregates which grow when the temperature decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458006
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation effects on Raman scattering from low-energy vibrational modes in glasses. II. Experimental results (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2046-2051 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: New experimental results of low-frequency Raman scattering from different glasses are presented. They are compared to the vibration density of states obtained from inelastic neutron scattering to deduce the light-vibration coupling coefficient C(ω) as a function of the vibration frequency. It was found that C(ω)∝ω2 at very low frequency ω〈20 cm−1 in inorganic glasses (SiO2,B2O3) and that C(ω)∝ω at low frequency in polymer glasses and in inorganic glasses for ω(approximately-greater-than)20 cm−1. Our experimental results for glasses are interpreted by assuming no correlation at very low-frequency and only radial correlation at low-frequency. A full correlation would exist in silica-aerogels in which the effect of random fluctuations would be negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465268
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation effects on Raman scattering from low-energy vibrational modes in fractal and disordered systems. I. Theory (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 2040-2045 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In disordered fractal or nonfractal systems, the disorder induces rapid fluctuations of the acoustical vibrational wave functions, so that statistics can be used to resolve the problem of Raman scattering from localized low-energy vibrations. We derive the expressions of light-vibration coupling coefficient, C(ω), as a function of the frequency ω, in the case of the dipole-induced dipole mechanism of susceptibility fluctuation and for different types of correlation, from full correlation to no-correlation. The results are compared to the existing numerical calculations. The expressions of C(ω) are determined for other mechanisms of susceptibility fluctuations, depending on an interaction propagating in the fractal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465267
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison between light and neutron inelastic scatterings. The frequency linear behaviour of the light-vibration coupling coefficient
    Amsterdam : Elsevier
    Physica A: Statistical Mechanics and its Applications 201 (1993), S. 257-262 
    Details
    ISSN: 0378-4371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0378-4371(93)90420-9
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  • 6
    Electronic Resource
    Electronic Resource
    Radiation-Induced-Defects Localization in Single-Mode Optical Fibers (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 480-481 (Mar. 2005), p. 329-332 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We studied the defects at the origins of the permanent radiation-induced attenuation in four g-rays irradiated single-mode germanosilicate optical fibers (~1 MeV; 1.2 kGy; 0.3 Gy/s) in the spectral range 400 - 1700 nm. We determined the wavelength dependence of the following cladding codopant influences: germanium (0.3 %), phosphorus (0.3 %), fluorine (0.3 %) on the germanosilicate (13 %) fiber radiation responses. We identified some of the different color centersproduced by g-rays and we evaluated their localization in the fiber cross-section through the determination of the radial distribution of the radiation-induced absorption at 633 nm. We also evidenced the strong interactions between these three codopants. In particular, our results showed that the properties of the phosphorus-related color centers, which mainly determine the fiber infrared radiation sensitivity, are strongly influenced by the germanium- and fluorine-codoping
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/10/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.480-481.329.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Gamma and UV Radiation-Induced Color Centers in Optical Fibers (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 480-481 (Mar. 2005), p. 323-328 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Radiation-induced losses and paramagnetic centers were investigated in phosphorusdoped and P-free multimode germanosilicate optical fibers after g-rays (~1 MeV) and ultraviolet (5 eV) exposures. After both types of irradiation, the same defects seem to be responsible of the fiber absorption in the spectral range 400 to 1650 nm. In particular, the P1 centers and the Phosphorus Oxygen Hole centers are created in both cases in the phosphorus-doped fibers and explain the high permanent radiation-induced attenuation levels observed in this fiber type. Luminescence and electron spin resonance measurements (77 K, ~9.38 GHz) on irradiated samples confirm that the GeE’, SiE’ and NBOHC defects are also generated in the different irradiated samples. From this study, it seems that the pertinence of a multimode fiber for nuclear space or civil applications couldbe estimated through low-cost ultraviolet measurements
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/10/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.480-481.323.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Can biological homochirality result from a phase transition? (1995)
    Springer
    Origins of life and evolution of the biospheres 25 (1995), S. 211-217 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The problem of chiral purity in living organisms is still one of the prominent difficulties in the study of the origins of life. In particular the parity non-conservation known to occur in weak interactions could not be related to this lack of symmetry: these physical forces, though universal, are very weak and up to now no amplification process had been proposed. In 1991, A. Salam remarked that, due to the attractive character of the parity violating force in electro-weak interactions, a phase transition at low temperature should exist, leading eventually to enantiomeric purity. We undertook then a series of experimental tests, looking for a sizeable change in the optical activity of cystine molecules. We found no evidence for the phase transition down to 0.01 K. The interpretation of these negative results will be discussed, and future experiments proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581584
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